Single-nucleotide polymorphism in the human mu opioid receptor gene alters beta-endorphin binding and activity: possible implications for opiate addiction

Opioid drugs play important roles in the clinical management of pain, as well as in the development and treatment of drug abuse. The mu opioid receptor is the primary site of action for the most commonly used opioids, including morphine, heroin, fentanyl, and methadone. By sequencing DNA from 113 former heroin addicts in methadone maintenance and 39 individuals with no history of drug or alcohol abuse or dependence, we have identified five different single-nucleotide polymorphisms (SNPs) in the coding region of the mu opioid receptor gene. The most prevalent SNP is a nucleotide substitution at position 118 (A118G), predicting an amino acid change at a putative N-glycosylation site. This SNP displays an allelic frequency of approximately 10% in our study population. Significant differences in allele distribution were observed among ethnic groups studied. The variant receptor resulting from the A118G SNP did not show altered binding affinities for most opioid peptides and alkaloids tested. However, the A118G variant receptor binds beta-endorphin, an endogenous opioid that activates the mu opioid receptor, approximately three times more tightly than the most common allelic form of the receptor. Furthermore, beta-endorphin is approximately three times more potent at the A118G variant receptor than at the most common allelic form in agonist-induced activation of G protein-coupled potassium channels. These results show that SNPs in the mu opioid receptor gene can alter binding and signal transduction in the resulting receptor and may have implications for normal physiology, therapeutics, and vulnerability to develop or protection from diverse diseases including the addictive diseases.

Ventral medial prefrontal cortex neuronal ensembles mediate context-induced relapse to heroin

In a rat model of context-induced relapse to heroin, we identified sparsely distributed ventral medial prefrontal cortex (mPFC) neurons that were activated by the heroin-associated context. Selective pharmacogenetic inactivation of these neurons inhibited context-induced drug relapse. A small subset of ventral mPFC neurons formed neuronal ensembles that encode the learned associations between heroin reward and heroin-associated contexts; re-activation of these neuronal ensembles by drug-associated contexts during abstinence provoked drug relapse.

Differential effects of blockade of dopamine D1-family receptors in nucleus accumbens core or shell on reinstatement of heroin seeking induced by contextual and discrete cues

In humans, exposure to environmental contexts previously associated with heroin intake can provoke drug relapse, but the neuronal mechanisms mediating this relapse are unknown. Using a drug relapse model, we found previously that reexposing rats to heroin-associated contexts, after extinction of drug-reinforced responding in different contexts, reinstates heroin seeking. This effect is attenuated by inhibition of glutamate transmission in the ventral tegmental area and medial accumbens shell, components of the mesolimbic dopamine system. Here, we explored the role of dopamine of the accumbens in context-induced reinstatement by using the D1-family receptor antagonist SCH 23390 [R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride]. Rats were trained to self-administer heroin for 12 d; drug infusions were paired with a discrete tone-light cue. Subsequently, the heroin-reinforced lever pressing was extinguished in the presence of the discrete cue in a context that differed from the drug self-administration context in terms of visual, auditory, tactile, and circadian cues. When tested in the original drug self-administration context, systemic and medial or lateral accumbens shell SCH 23390 injections attenuated context-induced reinstatement of heroin seeking, whereas accumbens core SCH 23390 injections were ineffective. In contrast, core but not lateral or medial shell SCH 23390 injections attenuated discrete-cue-induced reinstatement in a nondrug context after extinction of lever presses without this cue. Results indicate that activation of medial and lateral accumbens shell D1-family dopamine receptors mediate context-induced reinstatement of heroin seeking and provide the first demonstration for a role of lateral shell dopamine in conditioned drug effects. Results also demonstrate novel dissociable roles of accumbens core and shell in context- versus discrete-cue-induced reinstatement of heroin seeking.

Effects of buprenorphine maintenance dose on mu-opioid receptor availability, plasma concentrations, and antagonist blockade in heroin-dependent volunteers

The clinical effectiveness of opioid maintenance for heroin dependence is believed to result from a medication's ability to decrease mu-opioid receptor (muOR) availability thereby replacing agonist effects, alleviating withdrawal symptoms and attenuating heroin effects. We empirically tested this hypothesis in five heroin-dependent volunteers who were successively maintained on 32, 16, 2, and 0 mg daily buprenorphine (BUP) tablet doses. We predicted and confirmed that higher BUP doses would decrease in vivo muOR availability (measured with PET and [(11)C]carfentanil), increase plasma levels of BUP and its metabolite nor-BUP, and decrease withdrawal symptoms and hydromorphone (HYD) responses. Relative to placebo, BUP significantly decreased mean (+/-SEM) whole-brain muOR availability 41+/-8, 80+/-2, and 84+/-2% at 2, 16, and 32 mg, respectively. Regions of interest (ROIs) (prefrontal cortex, anterior cingulate, thalamus, amygdala, nucleus accumbens, caudate) showed similar dose-dependent effects. Changes in muOR availability varied across ROIs (prefrontal cortex, 47% vs amygdala, 27%) at BUP 2 mg, but were more homogeneous across ROIs at BUP 32 mg (94-98%; except thalamus, 88%). Relative to placebo (0 ng/ml), peak plasma levels of BUP and nor-BUP were comparable and dose-dependent (0.5-1, 5-6, and 13-14 ng/ml at 2, 16, and 32 mg, respectively). muOR availability decreases were negatively correlated with BUP plasma level and positively correlated with questionnaire-based opioid withdrawal symptoms and attenuation of HYD symptoms. These findings suggest that high-dose BUP maintenance produces near-maximal muOR occupation, muOR availability correlates well with plasma levels, and BUP-related opioid symptoms and antagonist blockade exhibit concentration-effect relationships.

Methadone-related opioid agonist pharmacotherapy for heroin addiction. History, recent molecular and neurochemical research and future in mainstream medicine

In 1963, Professor Vincent P. Dole at the Rockefeller University formed a small team to develop a pharmacotherapy for the management of heroin addiction. They hypothesized that heroin addiction is a disease of the brain with behavioral manifestations, and not merely a personality disorder or criminal behavior and began to address the specific question of whether a long-acting opioid agonist could be used in the long-term maintenance treatment of heroin addiction. Over the next 35 years, many studies documented the safety, efficacy and effectiveness of methadone pharmacotherapy for heroin addiction, but Federal regulations and stigmatization of heroin addiction prevented implementation of treatment. Finally, in 1999, NIH published a report unequivocally supporting methadone maintenance pharmacotherapy for heroin addiction. Two other effective opioid agonist treatments have been developed: the even longer acting opioid agonist l-alpha-acetylmethadol (LAAM) has been approved for pharmacotherapy for heroin addiction, and still under study is the opioid partial agonist-antagonist buprenorphine-naloxone combination. A variety of studies, both laboratory based and clinical, have revealed the mechanisms of action of long-acting opioid agonists in treatment, including prevention of disruption of molecular, cellular and physiologic events and, in fact, allowing normalization of those functions disrupted by chronic heroin use. Recent molecular biological studies have revealed single nucleotide polymorphisms of the human mu opioid receptor gene; the mu opioid receptor is the site of action of heroin, the major opiate drug of abuse, analgesic agents such as morphine, and the major treatment agents for heroin addiction. These findings support the early hypotheses of our laboratory that addiction may be due to a combination of genetic, drug-induced and environmental (including behavioral) factors and also, that atypical stress responsivity may contribute to the acquisition and persistence of, as well as relapse to, use of addictive drugs.

Cannabidiol, a nonpsychotropic component of cannabis, inhibits cue-induced heroin seeking and normalizes discrete mesolimbic neuronal disturbances

There remains debate regarding the impact of cannabis on neuropsychiatric disorders. Here, we examined the effects of cannabidiol (CBD), a nonpsychoactive constituent of cannabis, on heroin self-administration and drug-seeking behavior using an experimental rat model. CBD (5-20 mg/kg) did not alter stable intake of heroin self-administration, extinction behavior, or drug seeking induced by a heroin prime injection. Instead, it specifically attenuated heroin-seeking behavior reinstated by exposure to a conditioned stimulus cue. CBD had a protracted effect with significance evident after 24 h and even 2 weeks after administration. The behavioral effects were paralleled by neurobiological alterations in the glutamatergic and endocannabinoid systems. Discrete disturbances of AMPA GluR1 and cannabinoid type-1 receptor expression observed in the nucleus accumbens associated with stimulus cue-induced heroin seeking were normalized by CBD treatment. The findings highlight the unique contributions of distinct cannabis constituents to addiction vulnerability and suggest that CBD may be a potential treatment for heroin craving and relapse.

Acupuncture in heroin addicts; changes in Met-enkephalin and beta-endorphin in blood and cerebrospinal fluid

In heroin addicts showing features of heroin withdrawal basal beta-endorphin levels were elevated in both blood and cerebrospinal fluid (CSF) and did not change during electroacupuncture, although this therapy suppressed the clinical features of withdrawal. Met-enkephalin levels were not elevated in blood or CSF before treatment. However, successful electroacupuncture was associated with a rise in CSF met-enkephalin levels in all patients studied, although concentrations in blood did not alter.

Relapse to cocaine- and heroin-seeking behavior mediated by dopamine D2 receptors is time-dependent and associated with behavioral sensitization

The sensitizing properties of drugs of abuse have been proposed to play an important role in the persistence of drug seeking behavior. We decided to evaluate the temporal relationship of dopamine D2 receptor-mediated drug seeking behavior and behavioral sensitization in animals with a history of cocaine and heroin self-administration. During early phases of withdrawal (<1 week), activation of dopamine D2 receptors with quinpirole resulted in robust, dose-dependent, reinstatement of (non-reinforced) responding in both cocaine- and heroin-trained rats. Cocaine and heroin seeking induced by quinpirole was associated with a dramatic enhancement of the psychomotor stimulant effects of the D2 agonist, indicating that sensitization to D2-mediated events had developed. During the late phase of withdrawal (>3 weeks), reinstatement of cocaine seeking by quinpirole was still apparent, but less robust. In heroin-trained rats, increases of responding were no longer observed. Interestingly, behavioral sensitization to quinpirole was still observed in cocaine-trained rats, but was absent in heroin-trained rats. Thus, it appears that dopamine D2 receptors have a time-dependent role in relapse to cocaine and heroin seeking which is strongly associated with a behaviorally sensitized state.

Ventral tegmental area BDNF induces an opiate-dependent-like reward state in naive rats

The neural mechanisms underlying the transition from a drug-nondependent to a drug-dependent state remain elusive. Chronic exposure to drugs has been shown to increase brain-derived neurotrophic factor (BDNF) levels in ventral tegmental area (VTA) neurons. BDNF infusions into the VTA potentiate several behavioral effects of drugs, including psychomotor sensitization and cue-induced drug seeking. We found that a single infusion of BDNF into the VTA promotes a shift from a dopamine-independent to a dopamine-dependent opiate reward system, identical to that seen when an opiate-naïve rat becomes dependent and withdrawn. This shift involves a switch in the gamma-aminobutyric acid type A (GABAA) receptors of VTA GABAergic neurons, from inhibitory to excitatory signaling.

Mining Affymetrix microarray data for long non-coding RNAs: altered expression in the nucleus accumbens of heroin abusers

Although recent data suggest that some long non-coding RNAs (lncRNAs) exert widespread effects on gene expression and organelle formation, lncRNAs as a group constitute a sizable but poorly characterized fraction of the human transcriptome. We investigated whether some human lncRNA sequences were fortuitously represented on commonly used microarrays, then used this annotation to assess lncRNA expression in human brain. A computational and annotation pipeline was developed to identify lncRNA transcripts represented on Affymetrix U133 arrays. A previously published dataset derived from human nucleus accumbens was then examined for potential lncRNA expression. Twenty-three lncRNAs were determined to be represented on U133 arrays. Of these, dataset analysis revealed that five lncRNAs were consistently detected in samples of human nucleus accumbens. Strikingly, the abundance of these lncRNAs was up-regulated in human heroin abusers compared to matched drug-free control subjects, a finding confirmed by quantitative PCR. This study presents a paradigm for examining existing Affymetrix datasets for the detection and potential regulation of lncRNA expression, including changes associated with human disease. The finding that all detected lncRNAs were up-regulated in heroin abusers is consonant with the proposed role of lncRNAs as mediators of widespread changes in gene expression as occur in drug abuse.

Three methods of opioid detoxification in a primary care setting. A randomized trial

BACKGROUND

Opioid detoxification in a primary care setting followed by ongoing substance abuse treatment may be appropriate for selected opioid-dependent patients.

OBJECTIVE

To compare three pharmacologic protocols for opioid detoxification in a primary care setting.

DESIGN

Randomized, double-blind clinical trial with random assignment to treatment protocols.

SETTING

A free-standing primary care clinic affiliated with drug treatment programs.

PATIENTS

162 heroin-dependent patients.

INTERVENTIONS

Three detoxification protocols: donidine, combined donidine and naltrexone, and buprenorphine.

MEASUREMENTS

Successful detoxification (that is, when study participants received a full opioid-blocking dose [50 mg] of naltrexone), treatment retention (8 days), and withdrawal symptoms.

RESULTS

Overall, 65% of participants (36 of 55) who received clonidine, 81% (44 of 54) who received combined clonidine and naltrexone, and 81% (43 of 53) who received buprenorphine were successfully detoxified. Retention did not differ significantly across the groups: 65% of participants (36 of 55) who received clonidine, 54% (29 of 54) who received combined clonidine and naltrexone, and 60% (32 of 53) who received buprenorphine. Participants who received buprenorphine had a significantly lower mean withdrawal symptom score than those who received clonidine or combined clonidine and naltrexone.

CONCLUSIONS

Participants in the combined clonidine and naltrexone group and those in the buprenorphine group were more likely to complete detoxification, although retention at 8 days did not differ among the groups. Participants who were assigned to the buprenorphine group experienced less severe withdrawal symptoms than those assigned to the other two groups.

Blockade of nucleus accumbens opiate receptors attenuates intravenous heroin reward in the rat

A quaternary derivative of naloxone, methyl naloxonium chloride (MN), was administered intracerebrally to rats trained to self-administer heroin intravenously. Increases in intravenous (IV) heroin self-administration rates were found following injections of low doses of MN into the nucleus accumbens (N.Acc), but not following injections of low doses of MN into the ventral tegmental area (VTA). These results were interpreted to suggest that the rewarding properties of IV heroin were decreased following N.Acc opiate receptor blockade. The relative insensitivity of the VTA to MN treatment was taken to suggest that VTA opiate receptors are either not essential or play a secondary role in mediating IV heroin self-administration. The present data support the notion that post-synaptic N.Acc opiate receptors play a crucial role in maintaining IV heroin self-administration.

Buprenorphine-induced changes in mu-opioid receptor availability in male heroin-dependent volunteers: a preliminary study

A principle of opioid pharmacotherapy is that high medication doses should occupy fractionally more opioid receptors that mediate heroin effects. In this preliminary study we examined in vivo mu opioid receptor (muOR) binding in three healthy opioid-dependent volunteers during maintenance on 2 and 16 mg sublingual buprenorphine (BUP) liquid, and after detoxification (0 mg) under double-blind, placebo-controlled conditions, and once in matched controls. Binding measures were obtained with the muOR-selective radioligand [11C]carfentanil (CFN) and PET 4 hrs after BUP administration. BUP induced dose-dependent reductions in muOR availability, 36-50% at 2 mg and 79-95% at 16 mg relative to placebo. Heroin abusers also had greater muOR binding potential in the inferofrontal cortex and anterior cingulate regions during placebo, compared to matched controls. Further studies are warranted to examine the relationship of muOR availability with BUP therapeutic actions, and the clinical implications of increased muOR binding during withdrawal.

Striatal dopamine D2 receptor binding and dopamine release during cue-elicited craving in recently abstinent opiate-dependent males

Opiate addiction is a chronic disorder characterized by relapse behaviour, often preceded by craving and anhedonia. Chronic craving and anhedonia have been associated with low availability of dopamine D2 receptors (D2Rs) and cue-elicited craving has been linked with endogenous dopamine release. We studied D2R availability and cue-elicited endogenous dopamine release in 12 abstinent opiate-dependent males and 18 age-matched male controls with [123I]IBZM SPECT. Craving was manipulated with a video containing heroin-related stimuli. Moreover, chronic craving, anhedonia and cue-elicited craving were measured. We found lower baseline D2R availability in opiate-dependent subjects than controls in the left caudate nucleus. D2R availability in the putamen correlated negatively with years of opiate use. Opiate-dependent subjects demonstrated higher dopamine release after cue-exposure in the right putamen than controls. Chronic craving and anhedonia were positively correlated with DA release. Treatment strategies that increase D2Rs may, therefore, be an interesting approach to prevent relapse in opiate addiction.

Increased density of guanine nucleotide-binding proteins in the postmortem brains of heroin addicts

OBJECTIVE

To directly evaluate the guanine nucleotide-binding (G) protein subunits alpha, beta, and gamma, which are involved in the signal transduction of opioid receptors, in the postmortem brains of heroin addicts who had died of an opiate overdose.

METHODS

Specimens of the frontal cortex (Brodmann's area 9) were collected from 11 heroin addicts and 10 control subjects without a history of drug abuse. The biochemical status of human brain G protein subunits during opiate dependence was studied by means of immunoblotting techniques. Solubilized G proteins were separated by gel electrophoresis, transferred to pyroxylin membranes (western blotting) labeled with specific antiserum samples, and quantitated by image analysis after enhanced chemoluminescence.

RESULTS

In the frontal cortex, relevant increases in the immunoreactivities of G alpha i 1/2 (19% +/- 4%, P < .005), G alpha o (29% +/- 7%, P < .005), and G alpha s (26% +/- 5%, P < .005) but not of G alpha i3 were found in heroin addicts compared with age- and sex-matched controls. Moreover, the amount of G protein beta-subunit immunoreactivity was also consistently increased (27% +/- 8%, P < .01) compared with controls in the same brain region. These G protein changes in the brains of human opiate addicts paralleled (with the exception of G alpha s) those obtained in the brains of morphine hydrochloride-dependent rats. The increase in G alpha s immunoreactivity that was observed in the rat brain only after the short-term morphine administration (24% +/- 3%, P < .005) suggests that the increase in G alpha s immunoreactivity in the brains of human addicts could be the cellular response to a deadly overdose of heroin.

CONCLUSIONS

Alterations in the density of specific Gi and Go protein subunits that are coupled to mu-opioid and other opioid receptors may be of clinical relevance in opiate tolerance, dependence, and abstinence syndrome.

Disrupting reconsolidation of conditioned withdrawal memories in the basolateral amygdala reduces suppression of heroin seeking in rats

Recent data from our laboratory have demonstrated that appetitive drug memories undergo protein synthesis-dependent reconsolidation in the basolateral amygdala (BLA), an area important in the formation of emotional memories. We here investigated the importance of the BLA in the reconsolidation of opiate conditioned withdrawal memories. Rats with bilateral cannulas implanted in the BLA were trained to respond for heroin (0.12 mg/kg, i.v.) under a seeking-taking schedule, which required responding on a seeking lever to gain the opportunity to self-administer heroin by a single response on a taking lever. After induction of opiate dependence with subcutaneously implanted, heroin-filled osmotic minipumps (3 mg x kg(-1) x d(-1) heroin), rats received five consecutive pairings of a conditioned stimulus (CS) (tone, light, and odor compound) paired with naloxone (0.10 mg/kg, s.c.)-precipitated withdrawal. We replicated our previous findings that heroin seeking is suppressed in the presence of the withdrawal-associated CS. However, infusion of Zif268 antisense oligodeoxynucleotide into the BLA before reactivation of the CS-withdrawal association abolished this conditioned suppression in a reactivation-dependent manner. We also report that reconsolidation of CS-withdrawal memories upregulates Zif268 protein in the basolateral but not central nucleus of the amygdala and that Zif268 knockdown occurs selectively in the BLA. These results demonstrate that drug withdrawal memories undergo protein synthesis-dependent reconsolidation in the BLA and suggest a common mechanism for the reconsolidation of both appetitive and aversive drug memories.

Methadone effects on zidovudine disposition (AIDS Clinical Trials Group 262)

Large numbers of injection drug users (IDUs) are infected with HIV and receive both methadone and zidovudine (ZDV) therapy. Pharmacokinetic interactions between these agents may effect drug efficacy, toxicity, and compliance. To confirm and expand previous studies that identified a potential interaction between ZDV and methadone, we performed a within-subject study to determine oral and intravenous ZDV pharmacokinetics in 8 recently detoxified, heroin-addicted patients with HIV disease before and after initiation of methadone treatment. Acute methadone treatment increased oral ZDV in the area under the curve (AUC) by 41% (p = .03) and intravenous ZDV AUC by 19% (p = .06). Clearance was reduced by 21% (p = .007) and 19% (p = .04), respectively. Chronic methadone treatment increased oral ZDV AUC by 29% (p = .15) and intravenous ZDV AUC by 41% (p = .05). Clearance was decreased by 26% for both routes (p = .02). Methadone levels remained in the therapeutic range during ZDV treatment. These effects resulted primarily from inhibition of ZDV glucuronidation, but also from decreased renal clearance of ZDV. This study confirms that methadone-maintained patients receiving standard ZDV doses experience greater ZDV exposure and may be at increased risk for ZDV side effects and toxicity. Increased toxicity surveillance and possibly reduction in ZDV dose are indicated when these two agents are given concomitantly.

Striatal H3K27 Acetylation Linked to Glutamatergic Gene Dysregulation in Human Heroin Abusers Holds Promise as Therapeutic Target

BACKGROUND

Opiate abuse and overdose reached epidemic levels in the United States. However, despite significant advances in animal and in vitro models, little knowledge has been directly accrued regarding the neurobiology of the opiate-addicted human brain.

METHODS

We used postmortem human brain specimens from a homogeneous European Caucasian population of heroin users for transcriptional and epigenetic profiling, as well as direct assessment of chromatin accessibility in the striatum, a brain region central to reward and emotion. A rat heroin self-administration model was used to obtain translational molecular and behavioral insights.

RESULTS

Our transcriptome approach revealed marked impairments related to glutamatergic neurotransmission and chromatin remodeling in the human striatum. A series of biochemical experiments tracked the specific location of the epigenetic disturbances to hyperacetylation of lysine 27 of histone H3, showing dynamic correlations with heroin use history and acute opiate toxicology. Targeted investigation of GRIA1, a glutamatergic gene implicated in drug-seeking behavior, verified the increased enrichment of lysine-27 acetylated histone H3 at discrete loci, accompanied by enhanced chromatin accessibility at hyperacetylated regions in the gene body. Analogous epigenetic impairments were detected in the striatum of heroin self-administering rats. Using this translational model, we showed that bromodomain inhibitor JQ1, which blocks the functional readout of acetylated lysines, reduced heroin self-administration and cue-induced drug-seeking behavior.

CONCLUSIONS

Overall, our data suggest that heroin-related histone H3 hyperacetylation contributes to glutamatergic transcriptional changes that underlie addiction behavior and identify JQ1 as a promising candidate for targeted clinical interventions in heroin use disorder.

Activator of G protein signaling 3 regulates opiate activation of protein kinase A signaling and relapse of heroin-seeking behavior

The nucleus accumbens (NAc) is central to heroin addiction. Activation of opiate receptors in the NAc dissociates G(i/o) into alpha and betagamma subunits. Galpha(i) inhibits cAMP production, but betagamma regulates several molecular pathways, including protein kinase A (PKA). We show in NAc/striatal neurons that opiates paradoxically activate PKA signaling by means of betagamma dimers. Activation requires Galpha(i3) and an activator of G protein signaling 3 (AGS3). AGS3 competes with betagamma for binding to Galpha(i3)-GDP and enhances the action of unbound betagamma. AGS3 and Galpha(i3) knockdown prevents opiate activation of PKA signaling. In rats self-administering heroin, AGS3 antisense in the NAc core, but not shell, eliminates reinstatement of heroin-seeking behavior, a model of human relapse. Thus, Galpha(i3)/betagamma/AGS3 appears to mediate mu opiate receptor activation of PKA signaling as well as heroin-seeking behavior.

Striatal dopaminergic and serotonergic markers in human heroin users

To establish whether chronic opiate exposure might impair brain dopaminergic or serotonergic function in humans, we assessed biochemical indices of monoaminergic neurotransmitter activity and integrity in post mortem striatum of nine chronic heroin users and 14 control subjects. Striatal levels of the vesicular monoamine transporter were normal, suggesting that the density of dopamine nerve terminals is not reduced in heroin users. In nucleus accumbens, levels of tyrosine hydroxylase protein (-25%) and those of the dopamine metabolite homovanillic acid (-33%) were reduced significantly together with a trend for decreased dopamine (-32%) concentration. These changes could reflect either a compensatory downregulation of dopamine biosynthesis in response to prolonged dopaminergic stimulation caused by heroin, or reduced axoplasmic transport of tyrosine hydroxylase. Striatal levels of serotonin were either normal or elevated whereas concentrations of the serotonin metabolite 5-hydroxyindoleacetic acid were decreased by 27-38%. Our data suggest that chronic heroin exposure might produce a modest reduction in dopaminergic and serotonergic activity that could affect motivational state and impulse control, respectively.

Morphine, morphine-3-glucuronide, morphine-6-glucuronide, and 6-monoacetylmorphine determined by means of atmospheric pressure chemical ionization-mass spectrometry-liquid chromatography in body fluids of heroin victims

Morphine, morphine-3-glucuronide (M3G), morphine-6-glucuronide (M6G), and 6-monoacetylmorphine (6-MAM) were isolated from body fluids using solid-phase extraction and determined by means of atmospheric pressure chemical ionization-mass spectrometry-liquid chromatography (APCI-LC-MS) in selected ion monitoring mode. The following ions were monitored: m/z 286 for morphine; m/z 286 and 462 for M3G and M6G; m/z 211, 268, and 328 for 6-MAM; and m/z 289 for morphine-d3 (internal standard). The recoveries ranged from 82 to 89% The limits of detection were as follows: 0.1 ng/mL (morphine), 0.5 ng/mL (6-MAM), and 1 ng/mL (M3G and M6G). The analytes were determined in samples taken from 21 heroin-overdose victims. Twenty-one blood samples, 11 cerebrospinal fluid (CSF) samples, 12 vitreous humor (VH) samples, and 6 urine samples were investigated. Blood concentrations (ng/mL) of morphine ranged from 8 to 1539, of M3G from 111 to 941, of M6G from 32 to 332, and of 6-MAM from 0 to 73. The levels of morphine were correlated with glucuronide values and with 6-MAM. The concentrations of morphine, M3G, and M6G in CSF were, as a rule, lower than in blood and lower in VH than in CSF. The concentrations of morphine and molar ratios of M6G-morphine in blood and CSF were correlated. Low ratios of M3G-morphine and M6G-morphine in blood of heroin-overdose victims indicated short survival time after drug intake.

Role of projections from ventral subiculum to nucleus accumbens shell in context-induced reinstatement of heroin seeking in rats

RATIONALE AND OBJECTIVE

In humans, exposure to contexts previously associated with heroin use can provoke relapse. In rats, exposure to heroin-paired contexts after extinction of drug-reinforced responding in different contexts reinstates heroin seeking. We previously demonstrated that the projections from ventral medial prefrontal cortex (vmPFC) to nucleus accumbens (NAc) shell play a role in this reinstatement. The ventral subiculum (vSub) sends glutamate projections to NAc shell and vmPFC. Here, we determined whether these projections contribute to context-induced reinstatement.

METHODS

We trained rats to self-administer heroin (0.05-0.1 mg/kg/infusion) for 3 h per day for 12 days; drug infusions were paired with a discrete tone-light cue. Lever pressing in the presence of the discrete cue was subsequently extinguished in a different context. We then tested the rats for reinstatement in the heroin- and extinction-associated contexts under extinction conditions. We combined Fos with the retrograde tracer Fluoro-Gold (FG) to determine projection-specific activation during the context-induced reinstatement tests. We also used anatomical disconnection procedures to determine whether the vSub → NAc shell and vSub → vmPFC projections are functionally involved in this reinstatement.

RESULTS

Exposure to the heroin but not the extinction context reinstated lever pressing. Context-induced reinstatement of heroin seeking was associated with increased Fos expression in vSub neurons, including those projecting to NAc shell and vmPFC. Anatomical disconnection of the vSub → NAc shell projection, but not the vSub → vmPFC projection, decreased this reinstatement.

CONCLUSIONS

Our data indicate that the vSub → NAc shell glutamatergic projection, but not the vSub → vmPFC projection, contributes to context-induced reinstatement of heroin seeking.

Opiate levels in hair

By means of radioimmunoassay-technique, hair samples of users, drug related fatalities, carcinoma patients receiving morphine and of experimental guinea pigs receiving codeine were investigated for opiates. The RIA-investigations require a minimum of material; our routine procedures need only 50 mg of hair. No correlation existed between administered doses of opiates and their concentrations in hair of both human and experimental animals. By sectioning the hair, the approximate period of drug use in man could be detected. However, these findings could not be confirmed by the animal experiments. The growth rate of the hair, diffusion and adhesion processes may influence the transport of drugs along the hair. External contaminations and washing procedures were shown to increase or diminish the drug concentration of the samples.

Heroin-Administered Mice Involved in Oxidative Stress and Exogenous Antioxidant-Alleviated Withdrawal Syndrome

Heroin has been shown to elevate dopamine (DA) level. It is well known that an increase in DA oxidative metabolism leads to increased reactive oxygen species (ROS) formation, and thus, ROS have been frequently associated with neuronal cell death due to damage to carbohydrates, amino acids, phospholipids, and nucleic acids. This study investigated whether there are oxidative stress and effects of exogenous antioxidants in heroin-administered mice. The heroin-dependent mice model was made via intraperitoneal injection. Oxidative damage of DNA, protein, and lipid was measured by analysis of single cell electrophoresis, the 2,4-dinitrophenylhydrazine method, and thiobarbituric acid method respectively. The activities of antioxidative enzymes and total antioxidant capacity were assayed by spectrophotometry. After administration with heroin, the mice not only showed decrease of total antioxidant capacity in serum and antioxidant enzymes such as superoxide dismutase, catalase, and glutathione (GSH) peroxidase in brain, but also exhibited the oxidative damages of DNA, protein and lipid. On the other hand, exogenous antioxidants could restrain the oxidative stress, even alleviate withdrawal syndrome in heroin-administered mice. Our results also imply a possibility that ROS may participate in the whole process of dependence and withdrawal of heroin. Therefore, strategies of blocking oxidative stress may be useful in the development of therapy for opiate abuse.